Market Makers

Market makers are firms that stand ready to buy and sell securities at any time during trading hours. They profit from the spread between their buy and sell prices, and in exchange, they shoulder the inventory risk that comes with committing capital to markets that don’t always move in their favor.

Why markets need market makers

In a dealer-less market, a buyer waiting to purchase 10,000 shares must wait for a seller willing to offer those exact shares. The buyer might wait for hours or days. A market maker eliminates this friction: they commit to buying and selling at any time, absorbing the mismatch between buyers and sellers. This is why high-frequency trading firms and traditional broker desks compete for market-making mandate. Without them, the cost of transacting—measured in time and price slippage—would be far higher.

How market makers earn

Market makers profit from the bid-ask spread, the difference between the price they pay for a stock and the price they charge when they sell it. On a highly liquid stock like Apple, the spread might be a penny per share. On a less-traded security, it can be 10 or 20 cents. A market maker buying at $150.00 and selling at $150.01 earns that spread on volume.

The catch: market makers often take losses too. If they buy 5,000 shares expecting to sell them quickly, but the price drops before they find a buyer, they lose on the inventory. Over time, market makers control this risk by setting their spread wide enough to cover expected losses from adverse selection—the cost of trading against better-informed traders.

Competing market-making models

Traditional dealers on exchange floors used to dominate. Today, competition comes from several directions. Electronic communication networks (ECNs) introduced automated market makers who could undercut traditional spreads. Algorithmic trading firms built speed advantages to scalp the spread faster. And passive index funds, by capturing the majority of retail flows, have reduced the need for aggressive market-making in many large-cap stocks.

The best execution rules require broker firms and exchanges to ensure customers receive fair pricing. This competition has tightened spreads dramatically over the past 20 years, benefiting retail traders—but at the cost of lower profit margins for traditional market makers.

Inventory management and hedging

Market makers don’t want to hold shares overnight if they can avoid it. Instead, they monitor their inventory minute by minute and adjust their quotes to balance supply and demand. If they build up a long position, they lower their asking price to encourage sales. If they’re short, they raise their bid to attract buyers.

When they can’t balance in real time—say, a 1,000-share block of an illiquid stock lands on their desk—they hedge by buying or selling index futures, or by short selling similar stocks. Sophisticated firms use statistical models to predict price movements and size their hedges accordingly.

Regulatory requirements

Market makers who quote prices on stock exchanges must register with the SEC and the Financial Industry Regulatory Authority (FINRA). Most major exchanges have formal market-maker designation, which carries obligations: the maker must maintain a continuous two-sided market, limit their bid-ask spread within bounds, and participate in opening and closing auctions. In exchange, they receive fee rebates or other incentives.

Exchanges use these rules to prevent market makers from simply quoting wide spreads and never trading. The goal is to ensure that opening and closing prices are fair, and that liquidity exists even in periods of uncertainty.

The decline of traditional market-making

For much of the 20th century, market-making was a guaranteed profit engine. A broker could quote a wide spread, execute trades slowly, and count on their inventory holding value. The rise of electronic markets, indices, and automated trading has changed that. Spreads have shrunk—often to a fraction of a penny. Retail brokers now offer commissionless trading, pushing brokers toward payment for order flow as an alternative revenue source. And competition from algorithmic traders means the survivors are those with the fastest systems and the lowest costs.